1. Field of the Invention
The present invention relates to a motor driving apparatus, and more specifically to a motor driving apparatus which stores regenerative power in a deceleration of a motor and discharges the stored power in an acceleration of the motor.
2. Description of the Related Art
In a motor driving apparatus, a great driving current runs for acceleration during the motor acceleration (powering) period, and a regenerative current is produced during the deceleration period. Therefore, the motor driving apparatus has to be designed in consideration of a peak current in the motor acceleration (power running) period, resulting in increased size and cost of the apparatus. Moreover, the regenerative current generated in the deceleration period is thermally consumed by a regenerative resistor, resulting in wasted energy loss.
As a countermeasure for solving the above problems, there is known an invention in which a capacitor is connected to a converter (rectification circuit) section for converting an AC power into a DC power, an inverter section for converting the DC power into the AC power to drive an AC motor, and a DC link that links the converter (rectification circuit) section to the inverter section. An electric power stored in the capacitor is supplied to the inverter section in the acceleration period, and a regenerative power is stored in the capacitor in the deceleration period, so as to equalizing a driving current and avoiding a waste of the regenerative current (refer to JP 2000-141440A).
It is effective for the miniaturization and laborsaving of the motor driving apparatus to provide the capacitor to store the regenerative power therein and supply the power from the capacitor to equalize the driving current during the motor acceleration period while keeping the capacitor voltage at a given value as described in the above JP 2000-141440A. On the other hand, however, the capacitor needs to be charged to the given voltage, and charging the capacitor requires a dedicated transformer and converter (rectification circuit). There is an idea of using the converter section of the motor driving apparatus both as a converter section and a converter (rectification circuit) and thus configuring the charging circuit of the capacitor at low cost. If the converter section of the motor driving apparatus is utilized by way of charging the capacitor, however, the performance (charging current) of charging the capacitor is determined by the performance of the converter (rectification circuit) section of the motor driving apparatus. This forces the development of a large number of charging circuits according to the type of the motor driving apparatus, thereby raising the development cost.